This invention relates to sorting tires according to a code assigned to a tire manufacturer by the Department of Transportation (DOT code), which is written in alphanumeric characters on a tire's outside circumferential surface. The code specifies pertinent details about the tire, and the sorting system sorts the tires according to one or more of the details of particular interest. For example, automobile and truck tires, which carry the alphanumeric code are sorted by the system which executes the same reading function a human would, were he to perform the same task.
More particularly the system of especial interest herein, is one for sorting green, that is uncured or unvulcanaized, tires which are presented to a tire painting machine in a profusion of sizes. "Green" tires are those which are to be cured by vulcanization in vulcanizing molds. The code may also identify the tire building machine on which the tire was constructed, and other vital data.
This system is peculiarly adapted to sorting tires which are desirably also capable of being sorted by a human. Thus, the system is to be used where a "bar graph", bar code, or magnetic encoding of the article has been ruled out, for one reason or the other. For example, though a bar code has excellent machine readability it would require a new tag to be placed on the tire, the tag would then have to be located before it is read, and the reliability of the system would hinge upon the conscientiousness of the tire builder who would be required to place the tag in a specified location, duly affixed without wrinkles, or stretch distortion, etc. Moreover, the bar code would be only machine readable even if it was directly inked on the tread, assuming it could be inked with a sufficient lack of distortion. Such a set of bar codes and magnetic codes would not be easily readable by purchasers of the tires who would likely disapprove of them.
The foregoing are the practical circumstances which surround the sorting of green tires which must be routed to particular curing presses. After the tires are cured, they retain the coded legend and can be checked by a human, if the need arises. This system is limited to the use of a line-scan camera which optically reads an alphanumeric code and uses the information through a series of logic circuit means, to eject designated articles. from a conveyor onto which the tires to be sorted are deposited.
Line-scan cameras of the type used are disclosed in U.S. Pat. Nos. 2,981,877; 3,015,048; 3,064,167; 3,108,359; 3,117,260; inter alia, the disclosures of which are incorporated by reference thereto as if fully set forth herein, and the cameras are commercially available as CCD Line-Scan Models CCD 1100, 1300, and 1400.
In the particular instance where an assortment of green tires in different sizes are to be sorted, the sequence of events in a tire plant should be noted. A tire is constructed on a tire building machine, after which it is placed on a conveyor which conveys it to a tire painting machine where inside and outside tire paints are sprayed onto the tire. Many other tires of different sizes and shapes are also placed on the same conveyor, all of which tires are to be painted with the same tire paints before the tires are vulcanized.
Tire paints are so termed because a thin film of a liquid dispersion is painted, then dried on the green tire. Without tire paints a vulcanized tire could not be removed from the vulcanizing mold without the tire being damaged. Such tire paints typically include a rubber latex, wax and carbon black, as disclosed for example in U.S. Pat. No. 4,329,265.
The tire painting machine is typically a paint spray booth in which elevatable spray guns are positioned to spray the paint on the inner surfaces of a tire, which inner surfaces are to be contacted with a pressurized heated bladder in the curing press, and on the outer surfaces of the sidewalls of the tire. Before the tire is painted, it is picked up by its upper bead, then rotated just before, and during the time when paint is sprayed from the guns. Further relevant details of the operation of the tire painting as it relates to providing information for the sorting of tires will be set forth hereinafter. The inner surfaces of the curing molds are also painted, not necessarily with the same paint, to facilitate release of the patterned tread from the mold.
After the tires are painted, they are deposited on a conveyor and mechanically sorted according to the inside diameter of their central bead openings, as described in U.S. Pat. No. 3,159,278. In many tire plants, green tires are sorted by humans who read the alphanumeric codes on the tread, then route the tires to be cured in the appropriate curing presses. The advantages and benefits of performing such a tedious and error-prone task by machine are evident.
Towards this end, several attempts have been made in the prior art to sort tires, as for example, those disclosed in U.S. Pat. Nos. 3,460,119 and 3,895,716, inter alia. But no prior art system was predicated upon the basis that it was to read a code which was printed by existing printing equipment, using conventional white ink to print an alphanumeric code with a standard character font on the tread, and without adding any tags or tape to the tire. More particularly, it was decided to read an existing code which consisted of alphanumeric characters of different sizes, only some of which were pertinent for the sorting task. Most notably, having made the decision to read the alphanumeric code, it appeared cavalier, or worse, to elect to read the code in a spray painting booth where visibility was never going to be all it should be.
Yet, this is precisely what the system does in the first of several steps delineated in greater detail hereinbelow, to provide a reliable and low cost method of sorting any article of arbitrary shape which can carry an alphanumeric code which can be read by a stationary line-scan camera, provided the article is to be subjected to a processing step, analogous in its procedural aspects to the painting step herein.